How Complete Is The Fossil Record?
For some species, there is a near perfect fossil record: almost every animal left a fossil. In other cases, we might find a clutch of huge fossilized eggs, but not find fossils of whatever laid them. Still other species left skewed records. A short summary just doesn’t do justice to this complicated situation. At any given time, some portion of the earth is being eroded away. Mostly, high regions erode, and the resulting bits and pieces get washed downhill. That all has to fetch up somewhere, so, some low-lying regions of the earth will be undergoing deposition. Any creature which lives in an erosion area is extremely unlikely to get buried, so we don’t find fossils of mountain goats. Any creature which lives in a deposition area can easily be buried, and it may leave a fossil, particularly if the area is anoxic. Unless, of course, it is a jellyfish, with no hard parts. Casts of soft creatures are truly rare. On the whole planet, there are only a dozen-odd important deposits showing th
